A gas turbine engine, typically used as a source of propulsion in aircraft or power generation, operates by drawing in ambient air, compressing that air in a compressor section, mixing and combusting the compressed air with a fuel, and then forcing the resulting exhaust gasses through a turbine. The compressor section typically includes a high and low pressure compressor, each having a plurality of rotating blades which rotate relative to a plurality of fixed vanes to compress the ambient air. A portion of the compressed air is used to cool a combustor of the engine while the rest is mixed with the fuel and ignited.
Typically, an igniter generates an electrical spark to ignite the air-fuel mixture. The products of the combustion and the remains of the air-fuel mixture then travel out of the combustor as exhaust and through a turbine section. The turbine section, having a high and low pressure turbine each with a plurality of blades extending from a center body, is forced to rotate as the exhaust passes through the turbine blades. The turbine section and the compressor section are connected to a pair of engine shafts concentrically mounted running through the center of the engine. Thus, as each turbine rotates from the exhaust, the corresponding compressor rotates to bring in and compress new air. Once started, it can thereby be seen that this process is self-sustaining.
Combustors for gas turbine engines typically have a combustor shell and a combustor liner inside the shell which thereby defines an air passage therebetween. More specifically, in an annular combustor there may be an outer shell and outer liner, an inner shell and inner liner with air passages between both sets of shells and liners.
The outer liner may be disposed radially inside the outer shell and the inner liner may be disposed radially outside of the inner shell. In addition, a combustion chamber is provided between the inner and outer liners. In such a combustor, typically at least one igniter is disposed in at least one opening provided through the outer combustor shell and the outer liner. In some combustors, the liners may be segmented into panels, with one panel of the outer liner being referenced to as an igniter panel, and which includes the at least one igniter opening.
To prevent the compressed air from outside of the combustion chamber, typically used for cooling the combustion chamber, from entering the combustion chamber through the igniter opening or opening, a seal is typically positioned around each igniter. But for such a seal, air could pass around the igniter and into the combustor chamber. This might detrimentally affect engine performance in terms of ignition of the air-fuel mixture, or disruption of the flow of the air-fuel mixture in the combustion chamber. The seal may also prevent combustion gases from escaping the combustion chamber into the area around the combustion chamber, which might also detrimentally affect engine performance.
In prior art engines, no extra cooling for the igniter and the area around the igniter was provided. However, as gas turbine combustion engines have advanced, temperatures in the combustion chamber, and more specifically the area around the igniter, have increased during operation. These increased temperatures can damage the outer liner and outer shell of the combustor. For example, a crack in the igniter panel and/or outer shell can form from excessive heating of the igniter panel and/or insufficient cooling. Such deformations of the igniter panel and/or shell can, among other things, cause degradation in the igniter operation, thereby necessitating the repair or replacement of engine components.